Figure 4.

Immune serum from DR3 mice immunised with selected SmD peptides and SmD_66–80 mimics peptides had diverse auto-antibodies (auto-Ab) specificities by ELISA. (A) Five SmD_66–80 bacterial mimics were chosen to immunise HLA-DR3 mice. These mimic peptides came from two commensal bacteria (SmD_66–80M2, M2 and SmD_66–80M5, M5), from two pathogenic bacterial (SmD_66–80M7, M7 and SmD_66–80M11, M11) and one from environmental bacteria (SmD_66–80M9, (M9). They have different binding affinities to HLA-DR3. The red aa are the same ones as the parent SmD peptide, and the blue ones are those with conservative substitutions. Black aa indicates substitutions from other aa. (B) Sera from DR3 transgenic mice immunised with SmD, SmD_57–71, SmD_66–80, SmD_91–119 and M2, M5, M7 and M9 were diluted at 1:100 and used in ELISA for their antibody activities. SmD induced Abs against the six systemic lupus erythematosus (SLE)-related autoantigens (auto-Ags). SmD_57–71 induced Ab to SmB, A-RNP and Ro52. SmD_66–80 induced Ab to SmD, SmB, A-RNP and Ro52. SmD_91–119 induced anti-peptide Ab (data not shown) but did not induce Ab to all six SLE-related Ags. Except for M7, the other three mimics induced Ab to all six Ags. M7 did not induce Ab to Ro60 and La. M11 did not make Ab to any of these auto-Ags (data not shown). (C) Absorption experiments with antisera (1/100 diluted) from mice immunised with M5, M7 and M9 showed shared B cell epitopes among SmD_66–80, M3, M5 and M9. All immune sera were obtained 90 days after the initial immunisation.